PHP regular expression to match multiple email ID formats

Question

I am trying to obtain the local part of an email ID using regex. The challenge here is that the local part comes in two different formats and I need to figure out which format I'm reading and prepare the alternate form of that email ID. As always the snippet of my code that does this is pasted below.

$testarray = array("[email protected]", "[email protected]", "[email protected]", "[email protected]", "[email protected]");

foreach($testarray as $emailID) {
  preg_match("/([\w\d]*)\.([\w\d]*)@gmail.com/", $emailID, $match);

  if ($match[2] == "tp") {
    $altform = $match[1] . "@gmail.com";
  } else {
    $altform = $match[1] . "[email protected]";
  }

  error_log("ALTERNATE FORM OF $emailID IS $altform");

}

The problem I'm facing here is I'm not getting the desired result as neither $match[1] and $match[2] match anything for "[email protected]".

Your regular expression is expecting a full stop \. character, you should test if preg_match() actually worked or not before trying to consume $match — Scuzzy
– Scuzzy, Commented Mar 23, 2017 at 5:21

Wiktor Stribiżew · Accepted Answer · 2017-03-23 08:09:03Z

1

You need to use an optional group around the dot + word chars subpattern, and then check if the group matched after executing the search:

foreach($testarray as $emailID) {
    $altform = "";
    if (preg_match("/(\w+)(?:\.(\w+))?@gmail\.com/", $emailID, $match))
    {
        if (!empty($match[2]) && $match[2] == "tp") {
            $altform = $match[1] . "@gmail.com";
        } else {
            $altform = $match[1] . "[email protected]";
        }
    }
    print_r("ALTERNATE FORM OF $emailID IS $altform\n");
}

See the online PHP demo.

Notes on the pattern:

(\w+) - Capturing group 1: one or more word chars
(?:\.(\w+))? - 1 or 0 occurrences (due to ? quantifier) of:
- \. - a dot
- (\w+) - Capturing group 2: one or more word chars
@gmail\.com - a literal string @gmail.com (note the . is escaped to match a literal dot).

answered Mar 23, 2017 at 8:09

Wiktor Stribiżew

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